This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to German Application No. P 100 19 324.2 filed on Apr. 19, 2000, the entire content of which is incorporated herein by reference.
The invention generally relates to bearing arrangements. More particularly, the present invention pertains to a method and device for monitoring a bearing arrangement, having at least one bearing, in a housing of a roller journal bearing of a roller in a continuous casting installation.
Metal coming from above from a casting die, which has been preformed and is still hot, is deflected by 90xc2x0 in a continuous casting installation and is then guided in the horizontal direction for further processing. Although the metal leaving the casting die is still hot, it is sufficiently solidified so that it is necessary to provide considerable force for performing the deflection by 90xc2x0 from the vertical to the horizontal direction. For this purpose, a roller arrangement is provided. The roller arrangement has a multitude of rollers and causes slow xe2x80x9cbendingxe2x80x9d of the metal billet.
The rollers in the roller arrangement are arranged in an appropriate frame. The rollers have a journal at each of their two ends which is seated in a housing. A bearing arrangement is provided between the housing and the bearing journal.
The quality of the continuous casting process, as well as its efficiency, is essentially determined by the ability of the bearing arrangement to function. It is thus necessary to ensure that no bearing damage occurs over time. This can be accomplished through use of preventive maintenance at fixed intervals of time.
However, performing preventative maintenance at specified time intervals invariably results in the performance of preventive maintenance at times when the bearing does not necessarily require such maintenance.
A need thus exist for a method and associated device for monitoring a bearing arrangement of a bearing (e.g., roller journal bearing) of a roller in a continuous casting installation in a way that makes it possible to control the upkeep, maintenance and/or restoration of the bearing arrangement, as well as its surroundings, in such a way that the upkeep, maintenance and/or restoration is generally only actually triggered when there is a real need.
One aspect of the invention involves a method for monitoring a bearing arrangement of a roller journal bearing of a roller in a continuous casting installation that includes measuring a value of a process quantity at the bearing or in an area adjoining the bearing, providing an evaluation device with the measured value of the process quantity, comparing the measured value with a stored preset value, and triggering a signal when the measured value exceeds or falls below the stored preset value.
The present invention is thus based on the discovery that a process quantity associated with a bearing device of a roller journal bearing of a roller in a continuous casting installation is characteristic of the roller journal bearing""s ability to function, or of the operational dependability of the roller journal bearing. By monitoring or measuring the process quantity through use of a suitable sensor, the measured or monitored value of the process quantity can then be compared, preferably on a permanent and ongoing or continual basis, with a maximum or minimum threshold value which has been stored in a memory as a marginal threshold value required for the orderly operation of the bearing arrangement. Through comparison of the actual value with the nominal or threshold value, it is possible to trigger or initiate a signal when a permissible tolerance range is exceeded, thus providing the operator of the continuous casting installation with a warning that maintenance or replacement work on the respective roller journal bearing, or its surroundings, is necessary.
In accordance with one version of the present invention, the process quantity that is monitored is the force acting on the bearing. This can include the force acting in the axial direction of the bearing and/or the force acting in the radial direction of the bearing. Various force measuring bearings for measuring these forces are known in the art and used in other contexts. The stored threshold value for the maximum possible bearing force would be of such a magnitude that a response of the monitoring system, i.e., the triggering of a signal, occurs if, for example, forces act on the roller bearing reach an inadmissible magnitude. This could be due to, for example, wear in the vicinity of the bearing or could be due to other irregularities such as a tilted roller positioning in the frame.
Further, as an alternative to monitoring the force acting on the bearing, or in addition to monitoring such force, the monitored or measured process quantity can be the moisture in the bearing, or the moisture content of the lubricant in the bearing. It has been found that bearing damage occurs if an inadmissibly high amount of moisture is contained in the bearing. It is thus possible through use of a moisture sensor to measure and monitor the moisture at suitable positions of the bearing or in the surroundings of the bearing. The monitored or measured value of the moisture can then once again be compared to a stored threshold value so that if the monitored or measured value exceeds the stored value, a signal or warning is issued indicating that maintenance or replacement work on the respective roller journal bearing, or its surroundings, is required.
It is further possible as an alternative to, or in addition to, monitoring the force acting on the bearing and/or the moisture as described above, to monitor or measure the temperature prevailing in the bearing. In this connection the temperature of the outer ring is primarily considered because it can be measured in a relatively simple manner.
As an alternative to or in addition to one or more of the process quantities mentioned above, the process quantity on which monitoring is based can be the elastic or plastic deformation of the housing. In this case, the deformation can be measured in the circumferential direction of the housing, which thus provides a value indicating the ovalness of the housing, or can be measured in the axial direction of the housing. In the latter case the cylindrical characteristics of the housing are monitored. The deformation of the housing to be measured here typically occurs in the form of a superimposition of elastic, and of possibly present plastic deformation. It has been found that when defined threshold values of the deformation of the housing are reached, the service life of the bearing is clearly reduced. Thus, monitoring the deformation of the housing provides a reliable indication of a required repair or restoration of the housing.
As an alternative to or in addition to one or more of the process quantities mentioned above, the process quantity that is monitored or measured can be the vibration amplitude and/or vibration frequency of a preset area of the bearing. It is also possible to monitor the vibration acceleration of a selected or preset area of the bearing. Monitoring or measuring the vibration property of a bearing, and preferably the statistical evaluation thereof (amplitudes, frequencies, accelerations), can be used as an indicator for deciding when it is necessary to service, or replace, the bearing.
A still further process quantity which can be monitored or measured as an alternative to or in addition to one or more of the process quantities mentioned above is the number of revolutions of a bearing. This can be of particular importance in case of continuous casting installations as normally the number of revolutions of the rollers is not subjected to any particular monitoring.
In accordance with the various aspects of the present invention described above, it is envisioned that the measured or monitored value can be transmitted in a wireless manner. In this regard, the transmission can take place by induction as well as by radio.
According to another aspect of the invention, a device for monitoring a bearing arrangement, having at least one bearing, in a housing of a roller journal bearing of a roller in a continuous casting installation includes at least one sensor which senses a process quantity at a bearing or in an area adjoining the bearing, a mechanism for conducting the measured value of the process quantity to an evaluation device, a mechanism for comparing the measured value with a stored preset value, and a mechanism for triggering a signal as soon as the measured value exceeds or falls below the stored preset value.
Depending on the particular application or context of use, the sensor for monitoring or measuring the process quantity at the bearing or in the area adjoining the bearing can be a force sensor, a moisture sensor, a temperature sensor, a deformation sensor (e.g., one or several wire strain gauges) and/or a velocity or acceleration sensor.
The bearing preferably is a rolling bearing, a double row swivel-joint roller bearing, or a single or double row toroidal bearing.
In accordance with a further development of the present invention, the mechanism for conducting the measured value of the process quantity to the evaluation device can transmit this value in a wireless manner, preferably by induction, infrared signals or radio waves.
It is possible by way of the present invention to monitor various process quantities at a roller journal bearing of a roller in a continuous casting installation, and to use the measured or monitored process quantity(s) to draw specific conclusions regarding the necessary time for taking certain measures, including servicing or replacing the bearing. It is thus possible to initiate suitable activities at the right moment for performing replacement of the bearing arrangement at the start of bearing damage. It is also possible to improve and better optimize the entire production process of the continuous casting installation.
The invention is also applicable to the housing and the area surrounding the housing in the frame itself. Here, too, is it possible by way of the described actions to ensure that a replacement part is installed at the right moment. Wear in the area of the roller journal bearing can be made noticeable by measuring and monitoring the process quantities in question, thus providing an automatic indication at the correct time that maintenance work is required. This can provide an increased dependability with respect to unplanned outages, as well as the possibility of directly identifying the source(s) of malfunctions.